1. Field of the Invention
The present invention relates to an inkjet recording method, an inkjet recording device, and an inkjet recorded matter.
2. Description of the Related Art
An inkjet recording system is a recording system where ink droplets are jetted from very minute nozzles to deposit on a recording medium, to thereby form characters or an image. This system has been recently widely used because formation of a full-color image is easier compared to other recording system, and an image of high resolution can be obtained with a device of a simple structure.
Properties of an ink are indicated by physical properties, such as a viscosity and surface tension. An obtainable image quality or wetting ability of the ink can be controlled by regulating these physical properties.
When ink droplets are jetted, a new meniscus is formed at a jet outlet at the same time as the ink droplet is jetted. During this operation, the surface tension of the ink varies depending on the time, such as when a meniscus is started to be formed at the jet outlet, just before the ink droplet is jetted, the moment when the ink droplet is jetted, during jetting, the moment when the ink droplet is landed on a recording medium, and when the ink penetrates into the recording medium. Especially, the surface tension of the ink in the state where the motion thereof is slow, almost regarded as static, such as when a new meniscus is formed at the jet outlet, and when the ink is penetrates into the recording medium, and the surface tension of the ink in dynamic state where the motion thereof is fast, such as the moment when the ink droplets are jetted, are significantly different. Accordingly, when the properties of the inkjet recording ink are evaluated, it is important to consider the dynamic surface tension, which is surface tension in the dynamic state, as well as the static surface tension.
Typically, the static surface tension of the ink is preferably relatively low, as the static surface tension is related to the penetrating ability of the ink into a recording medium. On the other hand, the dynamic surface tension of the ink is related to jet stability of the ink, and therefore it needs to be certain strength. It has been known that these surface tensions of the ink can be controlled by a ratio of a surfactant or wetting agent added to the ink.
However, in accordance with the conventional controlling method, it has been difficult to secure certain strengths of both the static surface tension and the dynamic surface tension because the dynamic surface tension is reduced as the static surface tension is reduced, and in contrary, the static surface tension is increased, as the dynamic surface tension is increased. Therefore, there has been a problem that desirable jet stability and penetrating ability cannot be achieved at the same time.
Moreover, disclosed is a recording medium, such as an adhered concealing postcard, in which a releasable adhesive layer is provided on a surface of the recording medium after recording information on the surface of the recording medium by ink jet recording (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2001-219680). In the disclosed recording medium, the coating layer provided at the surface is adjusted so that the adhesive component stays on the surface when the adhesive is applied, which results in poor penetrating ability of the ink. In order to enhance penetrating ability of the ink relative to such recording medium for a concealing postcard, it is effective to reduce the static surface tension of the ink. However, if the static surface tension is reduced, the dynamic surface tension is also reduced, and therefore jetting performance becomes unstable. Accordingly, there has been no inkjet recording ink, which has excellent penetrating ability to the aforementioned recording medium, and can form high quality images without blurring.
For the purpose of providing an ink composition capable of forming a high quality recording image, as well as having excellent jet stability, when it is used in an inkjet recording method, by regulating a relationship between dynamic surface tension in the state where a motion is fast and static surface tension in the state where a motion is slow, an ink set is disclosed, and in the disclosed ink set, differences in dynamic surface tension between the inks are regulated at surface life time of 100 ms and 1,000 ms (see, for example, JP-A No. 2004-168793).
However, in this literature, there is no countermeasure for a problem that the ink has low penetrating ability to the recording medium, and a problem of achieving both jet stability and penetrating ability has not been solved. Moreover, this ink set is not designed to be used on a recording medium for a concealing postcard, and thus there is a problem that a high quality image cannot be formed on a medium for a concealing postcard.